The present invention relates to an improved process for the preparation of benzoxazin-4-one polymer conjugates. The process of the present invention provides for one-pot high yield conversion of an anthranilate and a polymeric component to proteolytic and/or lipolytic enzyme inhibitors useful in preventing skin irritation caused by endogenic proteolytic and/or lipolytic enzymes, inter alia, trypsin, chymotrypsin, elastase, pancreatic lipase, which comprise human feces.
Man-made enzyme inhibitors are widely used to modulate or inhibit the activity of enzymes. Control of enzymes has become critical in the prevention of skin irritation which is caused by the exposure of human skin to endogenic or exogenic enzymes. Particularly infants and incontinent adults have their skin routinely exposed to urine and feces which comprise proteolytic and/or lipolytic enzymes, inter alia, trypsin, chymotrypsin, elastase, pancreatic lipase. These enzymes promote skin degradation and therefore, might lead to discomfort.
Certain enzyme inhibitors have been successfully combined with polymeric materials to form benzoxazin-4-one polymer conjugates which modulate enzyme activity on exposed human skin while simultaneously providing the benefit of not being absorbed into the skin of the user. The process for preparing these polymer conjugates involves several discrete synthetic steps each of which involves isolation of a reaction intermediate or the use of reagents or solvents which present safety and cost issues.
There is therefore a long felt need for a process for forming a benzoxazin-4-one polymer conjugate which provides a direct, cost effective, and safe route.
The present invention meets the aforementioned needs in that it has been surprisingly discovered that benzoxaxine-4-one polymer conjugates can be prepared by way of a direct synthesis which provides the formulator with a more facile, cost effective, and safer route. The improvement over our own prior art synthesis precludes the use of more hazardous solvents, inter alia, methylene chloride, and affords the desired polymer conjugate in high yield.
The process of the present invention comprises the steps of:
a) reacting a polymer or copolymer having the formula:
Rxe2x80x94OH
wherein R is a hydrocarbyl moiety, a polyalkyleneoxy moiety, or a heteroatom comprising hydrocarbyl moiety, said polymer or copolymer having a molecular weight of from about 500 daltons, with phosgene to form a chloroformate having the formula: 
b) combining a substituted or unsubstituted anthranilic acid having the formula: 
wherein each R1 unit is an enzyme interaction attenuating unit; and a base catalyst wherein said base catalyst is a supported base catalyst, to form a substrate reactive admixture; and
c) adding to said chloroformate formed in step (a) said substrate reactive admixture formed in step (b) to form a benzoxazin-4-one conjugate having the formula: 
The process of the present invention also relates to the use of an auxiliary chloroformate, inter alia, a lower alkyl chloroformate to affect the benzoxazin-4-one ring closure.
The process of the present invention further relates to reacting a polymer or copolymer having the formula:
HOxe2x80x94Rxe2x80x2xe2x80x94OH
which when reacted with an anthranilate forms a polymer conjugate having two benzoxazin-4-one moieties.
These and other objects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. All percentages, ratios and proportions herein are by weight, unless otherwise specified. All temperatures are in degrees Celsius (xc2x0 C.) unless otherwise specified. All documents cited are in relevant part, incorporated herein by reference.
The present invention relates to a process for preparing benzoxazin-4-one polymer conjugates. The following is a description of the essential elements of the present invention.
Step (a): Formation of a chloroformate. Conversion of a hydroxyl moiety comprising polymer or copolymer to a chloroformate is the first required step of the process of the present invention. The polymer or copolymer may comprise one or more hydroxyl moieties thereby yielding a polymer conjugate which comprises more than one benzoxazin-4-one unit. However, the formulator may form the polymer conjugate having more than one hydroxyl unit in a manner wherein only an average of one hydroxyl unit links to a benzoxazin-4-one.
A polymer or copolymer having the general formula:
Rxe2x80x94OH
wherein R is a hydrocarbyl moiety, a polyalkyleneoxy moiety, or a heteroatom comprising hydrocarbyl moiety, said polymer or copolymer having a molecular weight of from about 500 daltons, is reacted with phosgene to form a chloroformate having the formula: 
Phosgene in the form of a gas or as a solution, inter alia, 20% solution by weight in toluene. Preferably a stoichiometric amount of phosgene is used. One equivalent of phosgene is used for every equivalent of xe2x80x94OH unit which is present in the polymer or copolymer molecule. For example, a mono-hydroxy polymer or copolymer will require one equivalent of phosgene, however, a polymer or copolymer comprising two xe2x80x94OH moieties, as in the preparation of a bis-benzoxazin-4-one conjugate analog, inter alia, bis-2-(PEG 4000)-5-methyl4H-3,1-benzoxazin-4-one, said formation requires at lease two equivalents of phosgene.
Examples of two preferred embodiments of the present invention relate to reacting a mono-hydroxy containing polymer or copolymer with phosgene to form a mono-chloroformate and reacting a dihydroxy polymer or copolymer with phosgene to form a bis-chloroformate.
The mono-hydroxy polymers or co-polymers of the present invention have the general formula:
Rxe2x80x94OH
whereas the dihydroxy polymers or co-polymers have the general formula:
HOxe2x80x94Rxe2x80x2xe2x80x94OH
wherein Rxe2x80x2 is preferably a polyalkyleneoxy moiety further described herein below, however, for the purposes of the present invention the general formula:
Rxe2x80x94OH
stands equally well for mono- as well as poly-hydroxy comprising polymers or co-polymers unless otherwise indicated.
For the purpose of the present invention the term xe2x80x9chydrocarbyl moietyxe2x80x9d is defined herein as xe2x80x9cany organic moiety which is comprised of carbon and hydrogen atoms in addition to the oxygen atoms which comprise the xe2x80x94OH units present. The only heteroatoms or atoms other than carbon and hydrogen are those atoms which are oxygen atoms comprising the hydroxyl moiety or moieties which react with phosgene in the first step of the present invention process.xe2x80x9d
The polymers or copolymers of the present invention may comprise monomers all of which have a hydroxyl unit, for example the polymer having the general formula: 
The formulator can include within the scope of the present invention lower molecular weight alcohols which when combined with the enzyme inhibitor elements do not diffuse into the skin cells and are therefore suitable for use as conjugates. Non-limiting examples of lower molecular weight alcohols useful according to the present invention include:
a) CH3xe2x80x94(CH2)21xe2x80x94OH; 
c) HOxe2x80x94(CH2)36xe2x80x94OH; 
For the purposes of the present invention a xe2x80x9cpolyalkyleneoxy moietyxe2x80x9d is defined herein as a unit having the formula:
R2(OR3)xxe2x80x94
wherein R2 is hydrogen, C1-C22 alkyl, C2-C6 hydroxyalkyl, C6-C12 substituted or unsubstituted aryl, and mixtures thereof; preferably hydrogen, C1-C4 alkyl, C2-C4 hydroxyalkyl, said hydroxyalkyl having the formula HO(CH2)2-4-; more preferably hydrogen and methyl.
R3 is C2-C12 alkylene, phenylene, C1-C4 alkyl substituted phenylene, C7-C22 alkylenearylene, and mixtures thereof; preferably C2-C6 alkylene, more preferably C2-C6 alkylene, yet more preferably ethylene, 1,2-propylene, most preferably ethylene.
The index x has the value from about 10 to about 10,000; preferably x has a value such that the xe2x80x9cpolyalkyleneoxy moietyxe2x80x9d has an average molecular weight of from about 500 daltons, preferably from about 1000 daltons, more preferably from about 2000 daltons, most preferably from about 3000 daltons to about 10,000 daltons, preferably to about 8,000 daltons, more preferably to about 7500 daltons.
Non-limiting examples of suitable polyalkyleneoxy polymers for use in the present invention include polyethyleneglycol having an average molecular weight of 1500 daltons (PEG 1500), 4000 daltons (PEG 4000), polyethyleneglycol having an average molecular weight of 5000 daltons (PEG 5000), polyethyleneglycol methyl ether having an average molecular weight of 1500 daltons (MPEG 1500), polyethyleneglycol methyl ether having an average molecular weight of 4000 daltons (MPEG 4000), polyethyleneglycol methyl ether having an average molecular weigh of 5000 daltons (MPEG 5000), block co-polymers of polyethylene glycol and polypropylene glycol (EO/PO co-polymers, wherein said PO unit can be 1,2-propylene, 1,3-propylene, or mixtures thereof), for example Pluronics(copyright) available ex BASF.
For the purposes of the present invention the term xe2x80x9cheteroatom comprising hydrocarbyl moietyxe2x80x9d is defined herein as any polymer or polymer conjugate which comprises one or more heteroatom, inter alia, nitrogen, other than an oxygen atom as described herein above for the definition of xe2x80x9chydrocarbylxe2x80x9d.
Preferred heteroatom units have the formula: 
wherein each R4 is independently
a) hydrogen;
b) C1-C4 alkyl;
c) substituted or unsubstituted phenyl;
d) substituted or unsubstituted benzyl;
e) carbocyclic;
f) heterocyclic;
g) and mixtures thereof;
each R5 is independently
a) hydrogen;
b) halogen
C) C1-C4 alkyl;
d) C1-C4 alkoxy;
e) substituted or unsubstituted phenyl;
f) substituted or unsubstituted benzyl;
g) carbocyclic;
h) heterocyclic;
i) and mixtures thereof;
each Z is independently
a) hydrogen;
b) hydroxyl;
c) halogen;
d) xe2x80x94(CH2)mR;
wherein R is:
i) hydrogen;
ii) hydroxyl
iii) halogen;
iv) nitrilo;
V) xe2x80x94OR6;
vi) or mixtures thereof;
each R6 is independently hydrogen, C1-C8 alkyl, C2-C8 hydroxyalkyl, and mixtures thereof;
the index m is from 0 to 6.
A non-limiting example of a xe2x80x9cheteroatom comprising hydrocarbyl moietyxe2x80x9d includes the co-polymer having the formula: 
wherein the indices indicate the percentage of each monomer present.
In addition xe2x80x9cstar polymersxe2x80x9d are suitable as the heteroatom containing units. These polymers includ tetra functional block copolymers of polyethylene glycol and polypropylene glycol based on reaction between ethylene diamine and ethylene oxide and polypropylene oxide, for example Tetronics(copyright) available ex BASF; trifunctional block copolymers of polyethylene glycol and polypropylene glycol based on reaction between propylene glycol and ethylene oxide and propylene oxide, for example, Poly-G T(copyright) series available ex BASF; and hydroxy-terminated Starburst(copyright) dendrimer (PAMAM-OH) of generation 2, 3, or 4, available ex Aldrich.
Step (a) of the present invention is preferably conducted in the presence of a solvent although a solvent is not necessary for formation of the chloroformate. Non-limiting examples of solvents include dichloromethane, toluene, benzene, ethyl acetate, and mixtures thereof, preferably dichloromethane and toluene. One preferred embodiment of the present invention utilizes a mixture of solvents, inter alia, dichloromethane and toluene. When a solvent is to be used for step (a), it is convenient to use toluene since phosgene is commercially available as a solution in toluene. However, mixtures of solvents can also be used if necessary to solublize the polymer or copolymer or the resulting chloroformate.
Step (a) is conducted at any temperature which is adequate to facilitate the formation of the desired chloroformate, preferably from 0xc2x0 C., more preferably from 25xc2x0 C., most preferably from 40xc2x0 C. to preferably about 200xc2x0 C., more preferably about 110xc2x0 C. The addition of the phosgene can be followed by refluxing of the solution. Typically when the formation of the chloroformate is accompanied by the evolution of excess heat a cooling device can be employed, however, under some circumstances, inter alia, the use toluene as a solvent, it may be necessary to warm the reaction to insure completeness of reaction.
Preferably the source of phosgene is added to the polymer or copolymer, however, any order of addition which adequately forms the chloroformate is encompassed by the present invention. The use of nitrogen, argon, or other suitable gas to provide an inert atmosphere for the reaction of step (a) is optional, but preferred.
Step (b): Combining a substituted or unsubstituted anthranilic acid with a base catalyst. Forming a substrate reactive admixture by combining an anthranilate and a base catalyst is the second required step of the process of the present invention.
A substituted or unsubstituted anthranilic acid having the formula: 
wherein each R1 unit is an enzyme interaction attenuating unit; and a base catalyst wherein said base catalyst is a supported base catalyst, is combined to form a substrate reactive admixture.
Preferably each R1 is independently selected from the group consisting of:
a) hydrogen;
b) C1-C18 substituted or unsubstituted, linear or branched alkyl;
c) C3-C18 substituted or unsubstituted, linear or branched cycloalkyl
d) C2-C18 substituted or unsubstituted, linear or branched alkenyl;
e) C2-C18 substituted or unsubstituted, linear or branched alkynyl;
f) C6-C18 substituted or unsubstituted aryl;
g) C2-C18 substituted or unsubstituted heterocyclic alkyl;
h) C3-C18 substituted or unsubstituted heterocyclic alkenyl;
i) alkylenearyl having the formula:
xe2x80x94(R7)nxe2x80x94R8
wherein R7 is C1-C12 linear or branched alkylene, C2-C12 linear or branched alkenylene, or mixtures thereof; R8 is C6-C18 substituted or unsubstituted aryl, or mixtures thereof; n is from 1 to 16;
j) an amino unit having the formula:
xe2x80x94(CH2)mN(R9)2
wherein each R9 is independently C1-C18 substituted or unsubstituted, linear or branched alkyl; m is from 0 to 10;
k) a unit having the formula:
xe2x80x94R10xe2x80x94R11
wherein R10 is xe2x80x94(CH2)pxe2x80x94, wherein p is from 0 to 12;
R11 is:
i) C1-C18 substituted or unsubstituted, linear or branched alkyl;
ii) C3-C18 substituted or unsubstituted, linear or branched cycloalkyl
iii) C2-C18 substituted or unsubstituted, linear or branched alkenyl;
iv) C2-C18 substituted or unsubstituted, linear or branched alkynyl;
v) C6-C18 substituted or unsubstituted aryl;
vi) C2-C18 substituted or unsubstituted heterocyclic alkyl;
vii) C3-C18 substituted or unsubstituted heterocyclic alkenyl;
viii) xe2x80x94OR12; wherein R12 is C1-C4 alkyl, C6-C10 aryl;
ix) or mixtures thereof; and
1) mixtures thereof.
For the purposes of the present invention C2-C18 substituted or unsubstituted heterocyclic alkyl is defined as any ring comprising an atom other than carbon, inter alia, nitrogen, sulfur, oxygen. Non-limiting examples of heterocyclic alkyl rings include, morpholinyl, piperidinyl, pyrrolidinyl.
For the purposes of the present invention C3-C18 substituted or unsubstituted heterocyclic alkenyl is defined as any ring comprising a site of unsaturation and an atom other than carbon, inter alia, nitrogen, sulfur, oxygen. Non-limiting examples of heterocyclic alkenyl rings include oxazolyl, 1-pyrrolinyl, and indolyl.
Non-limiting examples of R1 are selected from the group consisting of hydrogen, methyl, ethyl, isopropyl, phenyl, benzyl, amidino, bi-phenyl, xe2x80x94OR12; wherein R12 is methoxy, and mixtures thereof.
The base catalyst which is used in step (b) of the present invention is preferably a supported base catalyst. Non-limiting examples of supported base catalysts include poly 4-(vinylpyridine), DOWEX basic amine resin, inter alia, DOWEX Marathon WBA(copyright) available ex Dow Chemical; Amberlite(copyright) IRA-67, Aberlyst(copyright) A-21 available ex Rohm and Haas; Duolite(copyright) A-7 available ex Aldrich.
Step (b) of the present invention is preferably conducted in the presence of a solvent although a solvent is not necessary. Non-limiting examples of solvents include dichloromethane, toluene, benzene, ethyl acetate, and mixtures thereof, preferably dichloromethane and toluene. One preferred embodiment of the present invention utilizes a mixture of solvents, inter alia, dichloromethane and toluene. When a solvent is to be used for step (b), it is convenient to use toluene since a higher temperature can be used to dissolve reagents. However, mixtures of solvents can also be used if necessary to solublize the anthranilate adduct.
Step (b) is conducted at any temperature which is adequate to facilitate the formation of the desired admixture. The final admixture may be a homogeneous solution or a slurry depending upon the needs of the formulator. One embodiment of the present invention conducts step (b) under anhydrous conditions, that is the reagents are dried or excess moisture is removed before combining.
The use of nitrogen, argon, or other suitable gas to provide an inert atmosphere for the reaction of step (b) is optional, but preferred.
Step (c): Formation of a benzoxazin-4-one conjugate. The reacting of the chloroformate from step (a) with the substrate reactive admixture of step (b) is the third required step of the process of the present invention.
The chloroformate and anthranilate are reacted together in the presence of a base, said base being added in step (b) of the present process. In a preferred process according to the present invention, two equivalents or more of chloroformate may be used for every equivalent of benzoxazin-4-one conjugate formed.
In another preferred embodiment of the present invention, an auxiliary chloroformate is used to facilitate ring closure. Without wishing to be limited by theory, the first equivalent of chloroformate reacts to form a carbamate. A preferred additional step (d) comprises adding an auxiliary chloroformate to an in situ formed carbamate, said carbamate being the reaction product of the chloroformate from step(a) and the anthranilate from step (b). For example, step (c) is conducted wherein one equivalent of a polymer or copolymer chloroformate is added to one equivalent of a substrate reactive admixture under conditions wherein an un-isolated carbamate is formed in situ having the formula: 
and ethyl chloroformate is then added as an auxiliary chloroformate. Without wishing to be limited by theory, the auxiliary chloroformate reacts with the free carboxyl unit, xe2x80x94CO2H, to form a mixed anhydride thereby facilitating ring closure and formation of the benzoxazin-4-one having the formula: 
wherein R is a polymer or copolymer moiety.
Step (c) and optional step (d) is conducted at any temperature which is adequate to facilitate the formation of the desired benzoxazin-4-one conjugate, preferably from 50xc2x0 C. to about 150xc2x0 C., more preferably to about 75xc2x0 C. The reagents may be added in any order, for example the chloroformate to the reactive admixture or vice versa. However, when employing step (d), use of an auxiliary chloroformate, the chloroformate from step (a) must be reacted with the anthranilate first. Step (c) and step (d) are preferably conducted under anhydrous conditions, that is steps (a) and (b) are conducted under anhydrous conditions and the conditions are maintained throughout the procedure.
The use of nitrogen, argon, or other suitable gas to provide an inert atmosphere for the reaction of step (c) and (d) is optional, but preferred.
The polymer conjugate once formed is preferably isolated and purified, but isolation and purification is not necessary.
Non-limiting examples of auxiliary chloroformates which are useful in optional step (d) include methyl chloroformate, ethyl chloroformate, isobutyl chloroformate, and the like.
A general example of a preferred embodiment of the present invention comprises the steps of:
a) reacting a polymer or copolymer having the formula:
R2(OR3)xOH
wherein R2 is methyl; R3 is ethylene; x has the value from about 10 to about 225, in the presence of toluene with a solution of phosgene in toluene to form a chloroformate having the formula: 
b) combining an anthranilic acid or derivative thereof having the formula: 
wherein each R1 unit is hydrogen or methyl; and poly 4-vinylpyridine to form a substrate reactive admixture;
c) adding to said substrate reactive admixture formed in step (b) said chloroformate from step (a) to form a benzoxazin-4-one conjugate having the formula: 
A preferred embodiment of the above process comprises the steps of:
c) adding to one equivalent of said substrate reactive admixture formed in step (b) one equivalent of said chloroformate from step (a) to form a carbamate having the formula: 
d) reacting said carbamate with an auxiliary chloroformate to form a benzoxazin-4-one conjugate having the formula: 